1. Field of the Invention
The present invention concerns a filter arrangement for filtering x-rays, in particular for use in a mammography apparatus. The invention furthermore concerns an x-ray filter for such a filter arrangement.
2. Description of the Prior Art
Medical examinations of the soft tissue of the human breast that serve for early detection of breast cancer are implemented with x-ray radiation with a mammography apparatus. The breast to be examined is clamped between a subject table and a compression plate that can be shifted in position relative to the subject table. An x-ray examination is subsequently implemented with the irradiation unit, namely an x-ray radiator. A diaphragm is arranged to limit the x-ray beam by masking regions thereof. Furthermore, a filter arrangement, with typically a number of different filters, is provided between the x-ray radiator and the diaphragm. The individual filters serve for filtering out frequencies in the x-rays that are not required for the particular x-ray acquisition. An x-ray detector struck by the x-ray beam emitted from the irradiation unit strikes is integrated into the subject table. Soft x-ray radiation in the range below 50 kV (in particular under 30 kV) is used in the irradiation.
In the filter arrangement, filter foils made from various materials (for example rhodium or molybdenum) are glued onto a structure known as a filter wheel. In the case of a defective filter, an exchange is possible only with difficulty.